Nonwoven webs having improved necking uniformity

ABSTRACT

A neckable nonwoven web is provided with a central region and two edge regions, the central region being selectively easier to neck than the two edge regions. The nonwoven fibers in the central region have a polymer composition and/or physical properties which differ from the nonwoven fibers in the two edge regions. The selectively easier necking in the central region causes the central region to neck to about the same extent as the two edge regions, which otherwise would experience greater necking than the central region if the starting nonwoven web were completely uniform. Necked nonwoven webs and neck-bonded laminates made using the improved neckable nonwoven web, are also provided.

FIELD OF THE INVENTION

[0001] This invention is directed to nonwoven webs which, when exposedto a necking process, exhibit improved necking uniformity across thecross-directional width of the webs. The resulting necked nonwoven webshave more uniform basis weights across their width, compared toconventional necked nonwoven webs which tend to have a lower basisweight in the central region than in both edge regions.

BACKGROUND OF THE INVENTION

[0002] Necked nonwoven webs, including necked spunbond webs, meltblownwebs, combinations, and the like, are often made using a process whichis schematically illustrated in FIG. 1. A nonwoven web 12 having astarting width A is passed in its machine direction between a first nip16, which can be a first pair of nip rollers traveling at a firstsurface velocity, and a second nip 26, which can be a second pair of niprollers traveling at a second surface velocity which is faster than thefirst surface velocity. The surface velocity difference between thefirst and second nips results in formation of a narrower (“necked”)nonwoven web 22 having a necked width A′ which is less than the startingwidth A. The second average surface velocity is about 1.05-1.7 times thefirst average surface velocity, suitably about 1.1-1.5 times the firstaverage surface velocity, desirably about 1.2-1.4 times the firstaverage surface velocity.

[0003] The necked nonwoven web 22 generally includes fibers which arecloser together and more aligned in the machine direction than thefibers of the starting nonwoven web 12, which can be more randomlyaligned. While compacting and aligning the fibers, the necking processgenerally does not stretch individual fibers. The necking may beperformed with the aid of heat applied below the melting temperature ofthe fibers, for instance, by placing an oven or other heat sourcebetween the first and second nips. The necked nonwoven web 22 may alsobe heat set, either during or after the necking process, so that thenecked web becomes somewhat stable. A nonwoven web which is stable inthe necked condition is said to be “reversibly necked.” A reversiblynecked nonwoven web can be easily extended in the cross direction byapplying a small extension force, and tends to return to its narrower,necked configuration when the extension force is released.

[0004] The starting nonwoven web 12 includes edge regions 13 and 15, anda central region 11. The necked nonwoven web 22 includes edge regions 23and 25, and a central region 21. Because the necking causes the nonwovenfibers to become closer together and more aligned, without noticeablystretching or narrowing the individual fibers, the necked nonwoven web22 generally has a higher basis weight than the starting nonwoven web12.

[0005] As can be easily seen from FIG. 1, the nonwoven fibers in theedge regions 13 and 15 of the starting nonwoven web are subject todifferent strain, and travel a greater distance between the first nip 16and the second nip 26 of the necking process, than the fibers in thecentral region 11. Furthermore, the cross-directional stresses in thecentral region 11 are at least partially counteracted, because thesestresses are applied in both cross directions. The cross-directionalstresses in each of the edge regions 13 and 15 are primarily in onedirection, inward toward the center of the web. This results inincreased fiber gathering and necking in the edge regions. Consequently,the fibers in the edge regions 23 and 25 of the necked nonwoven web aregenerally more aligned and closer together than the fibers in thecentral region 21. As a result, the necked nonwoven web may benonuniform in the cross direction, having a higher basis weight in bothedge regions than in the central region, and having greatercross-directional extendibility in both edge regions than in the centralregion.

[0006] There is a need or desire for neckable nonwoven materials whichproduce necked nonwoven webs having better cross-directional uniformity.There is also a need or desire for necked nonwoven webs, and laminatescontaining necked nonwoven webs, which have better cross-directionaluniformity.

DEFINITIONS

[0007] As used herein, the term “recover” refers to a contraction of astretched material upon termination of a biasing force followingstretching length of the material by application of the biasing force.For example, if a necked material having a relaxed, unbiased width ofone (1) inch is elongated 50 percent in the cross direction bystretching to a width of one and one half (1.5) inches the materialwould be elongated 50 percent (0.5 inch) and would have a stretchedwidth that is 150 percent of its relaxed width. If this exemplarystretched material relaxed, and recovered to a width of one and onetenth (1.1) inches after release of the biasing and stretching force,the material would have recovered 80 percent (0.4 inch) of its one-half(0.5) inch elongation. Recovery may be expressed as [(maximum stretcheddimension minus final sample dimension)/(maximum stretched dimensionminus initial sample dimension)]×100.

[0008] As used herein the term “nonwoven web” means a web that has astructure of individual fibers or threads which are interlaid, but notin an identifiable repeating manner. Nonwoven webs have been, in thepast, formed by a variety of processes such as, for example,melt-blowing processes, spunbonding processes and bonded carded webprocesses.

[0009] As used herein the term “microfibers” means small diameter fibershaving an average diameter not greater than about 100 microns, forexample, having a diameter of from about 0.5 microns to about 50microns, more specifically microfibers may also have an average diameterof from about 4 microns to about 40 microns.

[0010] As used herein, the term “interfiber bonding” means bondingproduced by thermal bonding or entanglement between the individualnonwoven fibers to form a coherent web structure. Fiber entangling isinherent in the meltblown processes but may be generated or increased byprocesses such as, for example, hydraulic entangling or needlepunching.One or more thermal bonding steps are employed in most processes forforming spunbond webs. Alternatively and/or additionally, a bondingagent can be utilized to increase the desired bonding and to maintainstructural coherency of the web. For example, powdered bonding agentsand chemical solvent bonding may be used.

[0011] As used herein, the term “meltblown fibers” means fibers formedby extruding a molten thermoplastic material through a plurality offine, usually circular, die capillaries as molten threads or filamentsinto a high velocity gas (e.g., air) stream which attenuates thefilaments of molten thermoplastic material to reduce their diameters,which may be to microfiber diameter. Thereafter, the meltblown fibersare carried by the high velocity gas stream and are deposited on acollecting surface to form a web of randomly dispersed meltblown fibers.Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241 toButin, the disclosure of which is hereby incorporated by reference.

[0012] As used herein, the term “spunbonded fibers” refers to smalldiameter fibers which are formed by extruding a molten thermoplasticmaterial as filaments from a plurality of fine, usually circular,capillaries in a spinneret with the diameter of the extruded filamentsthen being rapidly reduced, for example, by eductive drawing or otherwell-known spun bonding mechanisms. The production of spunbondednonwoven webs is illustrated in patents such as, for example, in U.S.Pat. No. 4,340,563 to Appel et al., and U.S. Pat. No. 3,692,618 toDorschner et al. The disclosures of both these patents are herebyincorporated by reference.

[0013] As used herein, the term “different fibers” refers to fibers orgroups of fibers having different polymer compositions and/or physicalproperties, such that a first group of fibers is selectively easier toneck under set necking conditions than a second group of differentfibers.

[0014] As used herein, the term “necked material” refers to any materialwhich has been constricted in at least one dimension by processes suchas, for example, drawing or gathering.

[0015] As used herein, the term “neckable material” means any materialwhich can be necked.

[0016] As used herein, the “central region” of a nonwoven web is definedas the central 70% of the cross-directional width of the nonwoven web.The “edge regions” are defined as the outermost 15% of the width on bothsides of the central region of the nonwoven web.

[0017] As used herein, the term “reversibly necked material” refers to anecked material that has been treated while necked to impart memory tothe material so that, when a force is applied to extend the material toits pre-necked dimensions, the necked and treated portions willgenerally recover to their necked dimensions upon termination of theforce. One form of treatment is the application of heat. Generallyspeaking, extension of the reversibly necked material is substantiallylimited to extension to its pre-necked dimensions. Therefore, unless thematerial is elastic, extension too far beyond its pre-necked dimensionswill result in material failure. A reversibly necked material mayinclude more than one layer, for example, multiple layers of spunbondedweb, multiple layers of meltblown web, multiple layers of bonded cardedweb or any other suitable combination or mixtures thereof, as describedin U.S. Pat. No. 4,965,122, which is incorporated by reference.

[0018] As used herein, the term “percent neckdown” refers to the ratiodetermined by measuring the difference between the pre-necked dimension(width) and the necked dimension (width) of a neckable material and thendividing that difference by the pre-necked dimension of the neckablematerial.

[0019] As used therein, the term “percent stretch” refers to the ratiodetermined by measuring the increase in the stretched dimension (in anydirection) and dividing that value by the original dimension (in thesame direction) i.e., (increase in stretched dimension/originaldimension)×100.

[0020] As used herein, the term “composite elastic necked bondedmaterial” refers to a material having an elastic sheet joined to anecked material at least at two places. The elastic sheet may be joinedto the necked material at intermittent points or may be completelybonded thereto. The joining is accomplished while the elastic sheet andthe necked material are in juxtaposed configuration. The compositeelastic necked-bonded material is elastic in a direction generallyparallel to the direction of neckdown of the necked material and may bestretched in that direction to the breaking point of the neckedmaterial. A composite elastic necked-bonded material may include morethan two layers. For example, the elastic sheet may have necked materialjoined to both of its sides so that a three-layer composite elasticnecked-bonded material is formed having a structure of neckedmaterial/elastic sheet/necked material. Additional elastic sheets,necked material layers, and/or inherently extendible materials such asbonded carded webs may be added. Other combinations of elastic sheetsand necked materials may be used, for instance, as indicated in U.S.Pat. No. 5,336,545, which is incorporated by reference.

[0021] As used herein, the term “polymer” generally includes, but is notlimited to homopolymers, copolymers, such as for example, block, graft,random and alternating copolymers, terpolymers, etc. and blends andmodifications thereof. Furthermore, unless otherwise specificallylimited, the term “polymer” shall include all possible geometricalconfigurations of the material. These configurations include, but arenot limited to, isotactic, syndiotactic and random symmetries.

[0022] As used herein, the terms “selectively” encompass the terms“only” and “to a greater extent.”

[0023] As used herein, the term “consisting essentially of” does notexclude the presence of additional materials or process steps which donot significantly affect the desired characteristics of a givencomposition or product. Exemplary materials of this sort would include,without limitation, pigments, antioxidants, stabilizers, surfactants,waxes, flow promoters, solvents, particulates and materials added toenhance processability of the composition.

[0024] As used herein, the term “comprising” opens the claim toinclusion of additional materials or process steps other than thoserecited.

SUMMARY OF THE INVENTION

[0025] The present invention is directed to a neckable nonwoven materialhaving cross-directional nonuniformity which facilitates easier neckingin the central region of the nonwoven web than in the two edge regionsof the nonwoven web, and/or which selectively retards necking in theedge regions relative to the central region. The easier necking in thecentral region compared to the edge regions results in selectivelygreater than normal necking in the central region, sufficient to totallyor partially offset the greater necking in the edge regions whichinherently results from use of a conventional necking process. Thecross-directional nonuniformity resulting in easier necking in thecentral region can be achieved by varying the chemical (i.e., polymer)composition and/or physical characteristics of the central regionrelative to the two edge regions or vice versa.

[0026] The present invention is also directed to necked nonwoven websand laminates having more uniform necking and more uniform basis weightsand elongation in the cross direction, made using the neckable nonwovenmaterial of the invention.

[0027] Many nonwoven webs, including spunbond webs, are manufacturedusing an interfiber bonding process which bonds the adjacent fiberstogether at various locations according to a bonding pattern. In oneembodiment of the invention, the cross-directional nonuniformity of theneckable nonwoven material is accomplished by varying the interfiberbond pattern between the central region and the two edge regions in amanner which facilitates selectively easier necking in the centralregion. This can be accomplished by providing a lower percentage ofinterfiber-bonded area in the central region than in the two edgeregions. This, in turn, can be accomplished by a) providing bondpatterns which result in more free space between adjacent bonds in thecentral region than in the two edge regions, and/or b) varying thebonding intensity by bonding the central region at lower temperatureand/or pressure than are used to bond the edge regions.

[0028] In another embodiment of the invention, the physical propertiesof the fibers are varied between the central region and the two edgeregions of the nonwoven material, to facilitate easier necking in thecentral region. For instance, fibers which are thinner (with lower fiberdenier) may be provided in one region and fibers which are thicker (withhigher fiber denier) may be provided in the other region. Also, fiberswhich are more randomly or cross-directionally oriented may be providedin the central region, and fibers which are more machine-directionoriented may be provided in the two edge regions. Also, fibers which aremore circular may be provided in the central region, and fibers whichare less circular (have different shapes) may be provided in the twoedge regions. Also, fibers which are less compact (have lower bulkdensity) may be provided in the central region, and fibers which aremore compact (have higher bulk density) may be provided in the two edgeregions. Also, fibers which are crimped may be provided in the edgeregions but not in the central region, to selectively reduce necking inthe edge regions relative to the central region. Also, fibers which havebeen electrostatically treated following extrusion to cause betteralignment may be provided in the two edge regions, and fibers which havenot been electrostatically treated (and are less aligned) may beprovided in the central region.

[0029] In another embodiment of the invention, the chemical (i.e.,polymer) composition of the fibers in the central region is varied fromthe polymer composition of the fibers in the two edge regions. Polymerfibers having lower stiffness moduli generally neck more easily, and aremore suitable for the central region. For instance, polypropylene fibersmay be provided in the edge regions, while the central region may beprovided with a) polypropylene-polyethylene copolymer fibers, b)polyethylene fibers, c) mixtures of polypropylene fibers withpolyethylene fibers, d) fibers made from blends of polypropylene andpolyethylene, and/or e) polyethylene-polypropylene bicomponent fibers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030]FIG. 1 is a schematic illustration of a conventional neckingprocess, as described above.

[0031]FIGS. 2 and 3 are schematic illustrations of processes for makingneck-bonded laminates.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0032] Referring again to FIG. 1, a neckable nonwoven web 12 has acentral region 11 and two end regions 13 and 15. The central region 11has different physical properties and/or polymer composition than thetwo end regions 13 and 15, so that the central region has relativelyeasier necking.

[0033] As explained above, the central region is defined as the central70% of the lateral width of the nonwoven web, and the two edge regionsare defined as the outermost 15% of the lateral width on both sides ofthe central region. However, this does not mean that the boundariesbetween the nonwoven fibers which are selectively easier to neck, andthe fibers which are harder to neck, must occur precisely at the edges17 and 19 of the central region. These boundaries may occur inward oroutward of the edges 17 and 19 of the central region, so long as thecentral region is, on average, easier to neck than the two edge regions.

[0034] For instance, the boundaries between fibers which are selectivelyeasier to neck and those which are harder to neck may be located about2% to about 40% the total distance (based on 100% total lateral width)inward from edges 27 and 29 of the nonwoven web 12, suitably about 5% toabout 30% of the total distance inward from edges 27 and 29, desirablyabout 10% to about 25% of the total distance inward from edges 27 and29. For a homogeneous nonwoven web, the portions which neck in moreconstitute roughly the outer 6 inches of the width on both sides of thenonwoven web, regardless of the starting web width. Thus, for purposesof the invention, the boundaries between fibers which are easier andharder to neck may desirably be about 6 inches from the edges of thestarting material.

[0035] Alternatively, the physical properties and/or polymer compositionmay vary in a gradient fashion inward from the edges 27 and 29, with noprecise boundary between nonwoven fibers which are selectively easier toneck and those which are harder to neck. Regardless of whether there areboundaries or gradients, and regardless of where the boundaries areplaced the central region 11 of the nonwoven web 12 will, on average, beeasier to neck than the two edge regions 13 and 15.

[0036] In one embodiment of the invention, the interfiber bond patternbetween the central region and two edge regions is varied in a way whichfacilitates easier necking in the central region. For instance, thecentral region may have a lower percentage of interfiber bonding (basedon the planar area of the nonwoven fabric) than the two edge regions.Nonwoven fabrics suitable for necking typically have interfiber bondareas of about 1-50%. In accordance with the invention, the centralregion 11 may have an overall interfiber bond area which is at leastabout 3% less, suitably at least about 5% less, desirably at least about7% less than the overall bond area of the two edge regions 13 and 15.For example, if the two edge regions 13 and 15 (defined as the outer 15%on each side of nonwoven web 12) have an average bond area of 20%, thenthe central region 11 (defined as the central 70% of the nonwoven web12) should have an average bond area of 17% or less, suitably 15% orless, desirably 13% or less. One way to provide the edge regions 13 and15 to selectively greater bonding is to subject the edge regionsselectively to a hot air knife or similar secondary bonding process,after the nonwoven web has been formed and uniformly bonded according toconventional manufacturing techniques. Hot air knives are described inU.S. Pat. No. 5,707,468 to Arnold et al., which is incorporated byreference. Also, as explained above, the original bonding in the centralregion may be performed with lower temperature and/or pressure than inthe two end regions.

[0037] Alternatively, the central region 11 may be provided with arelatively less restrictive bond pattern, and the two edge regions 13and 15 may be provided with a relatively more restrictive bond pattern,between the nonwoven fibers. For purposes of necking, a less restrictivebond pattern may be one whose individual bonds are elongated andoriented more in the machine direction. A more restrictive bond patternmay be one whose individual bonds are elongated and oriented more in thecross direction. Elongated bond points may have a rectangular orelliptical shape, for instance, and may have an aspect ratio of at leastabout 2:1, desirably at least about 4:1. In one embodiment, bond pointshaving an aspect ratio of 4:1 may be oriented in the machine directionin the central region 11, and may be oriented in the cross direction inthe two edge regions 13 and 15. The orientation may shift all at once,or incrementally, between the central region and the two edge regions.In another embodiment, the central region may have a point bond patternwith widely spaced, larger points or dots, and the edge regions may havea dot bond pattern with more closely spaced, smaller points or dots. Ineither case, the average percent bond area may be the same for thecentral region and two edge regions, and the central region will haverelatively easier necking.

[0038] Alternatively, the central region 11 may be provided with thinnernonwoven fibers (of smaller average denier) than the nonwoven fibers inthe two edge regions 13 and 15. To accomplish selectively easier neckingin the central region, the fibers in the central region 11 should havean average fiber denier which is at least about 5% less, suitably atleast about 10% less, desirably at least about 20% less than the averagedenier of the fibers in the two edge regions 13 and 15. For example, ifthe average fiber denier in the two edge regions 13 and 15 is 5.0, thenthe average fiber denier in the central region 11 should be 4.75 orless, suitably 4.5 or less, desirably 4.0 or less. Fibers with loweraverage denier are less stiff, more pliable, and consequently easier toneck, than fibers of higher average denier. The different deniers may beprovided using spinneret dies having narrower and wider openings in thecentral and edge regions, respectively.

[0039] Alternatively, the central region 11 may be provided with fiberswhich are more randomly or cross-directionally oriented, and the twoedge regions 13 and 15 may be provided with fibers which are moremachine direction oriented. For instance, when the nonwoven (e.g.,spunbond or meltblown) web is manufactured, the edge regions may besubjected to higher velocity entrainment and quenching air streams thanthe central region, as the fibers exit the spinneret die. The highervelocity air causes greater straightening out (machine directionorienting) of fibers in the edge regions, relative to the centralregion.

[0040] Alternatively, the central region 11 may be provided with fiberswhich on average, are more round, and the edge regions 13 and 15 may beprovided with fibers which, on average, are less round (more shaped).The aspect ratio of a fiber is a ratio of the widest fiber diameter tothe narrowest fiber diameter. Completely round fibers have an aspectratio of 1.0. To achieve selectively easier necking in the centralregion, the average aspect ratio of fibers in the central region 11should be at least about 0.5 less, suitably at least about 0.75 less,desirably at least about 1.0 less than the average aspect ratio offibers in the edge regions 13 and 15. Round fibers are believed to bemore prone to necking, and less prone to physical deformation orstretching, than fibers which are flat or shaped.

[0041] Alternatively, the central region may be provided with fiberswhich are less compact, and have lower average bulk density, than fibersin the edge regions. To accomplish selectively easier necking in thecentral region, the central region 11 should have an average bulkdensity that is at least about 5% less, suitably at least about 10%less, desirably at least about 20% less than the average bulk density ofthe two edge regions 13 and 15. Fibers of lower bulk density generallyhave more space in between them, and are easier to displace and neck,than more compact fibers of higher bulk density. One way to vary thebulk density in the desired fashion is to selectively subject the edgeregions 13 and 15 to a compaction process. This can be accomplished bysubjecting the edge regions selectively to a pressurized calenderingprocess, or by subjecting the entire nonwoven fabric to a calenderingprocess having rollers shaped to provided relatively higher pressure inthe edge regions.

[0042] Alternatively, the edge regions 13 and 15 may be provided withnonwoven fibers which are crimped, and the central region 11 may beprovided with fibers which are less crimped or not crimped (or withmixtures of crimped and non-crimped fibers). The crimped fibers shouldhave a degree of crimping of at least four crimps per inch, suitably atleast six crimps per inch, desirably at least ten crimps per inch.Fibers having zero to less than four crimps per inch are considered tobe not crimped, for purposes of this invention. Fibers which are crimpedhave less tendency to neck in, because these fibers must substantiallystraighten out before they experience any significant necking tension.Already straight fibers buckle around each other, neck at an earlierstage, and ultimately neck more. To achieve selectively easier neckingin the central region 11, the central region 11 may be provided withfibers at least 60% of which are not crimped, and the edge regions 13and 15 may be provided with fibers at least 60% of which are crimped.Alternatively, the central region may be provided with fibers none ofwhich are crimped, while the edge regions are provided with fibers atleast 20% of which are crimped. Regardless of the percentages selected,the difference between the percentage of crimped fibers in the centralregion and the percentage of fibers in the two edge regions should be atleast about 10%, desirably at least about 20%, with the higherpercentage of crimped fibers existing in the edge regions.

[0043] Alternatively, the edge regions 13 and 15 may be provided withfibers that are generally more aligned than the fibers in the centralregion 11. This may be accomplished by electrostatically (e.g., corona)treating the fibers in the edge regions after they are extruded from aspinneret, before they contact a forming conveyor. The corona treatmentof fibers in the edge regions only causes them to be electrostaticallyattracted to each other and, thus, more aligned.

[0044] In another embodiment of the invention, the polymer compositionof the nonwoven fibers in the central region 11 is varied from thepolymer composition of the nonwoven fibers in the two edge regions 13and 15, so that the fibers in the central region have, on average, lessstiffness (lower moduli) than the fibers in the two edge regions. Toachieve selectively easier necking in the central region, the centralregion 11 may be provided with fibers at least 60% of which have a firstpolymer composition, and the edge regions 13 and 15 may be provided withfibers at least 60% of which have a second polymer composition, with thefirst polymer composition having a lower modulus than the secondcomposition. Alternatively, the central region may be provided withfibers entirely having the first composition, and the edge regions maybe provided with fibers at least 20% of which have the secondcomposition. Regardless of the percentages selected, the differencebetween the percentage of fibers in the central region having the firstcomposition of lower modulus, and the percentage of fibers in the edgeregions having the first composition, should be at least about 20%,suitably at least about 30%, desirably at least about 50%.

[0045] For instance, nonwoven web 12 may be formed from a combination ofsubstantially crystalline polypropylene fibers (formed frompolypropylene or a random propylene-ethylene copolymer containing up to10% by weight ethylene) and amorphous or semi-crystallinepropylene-ethylene copolymer fibers containing more than 10% ethylene,wherein the difference in ethylene contents between the two polymertypes is at least 5% based on total polymer weight. In accordance withthe invention, the central region should contain at least 20% by weightmore of the amorphous or semi-crystalline copolymer fibers (based on thetotal weight of the fiber mixture in the central region) than the twoedge regions (which would contain correspondingly higher amounts of thesubstantially crystalline polypropylene fibers). Suitably, the centralregion will contain at least 30% by weight more of the amorphous orsemi-crystalline copolymer fibers, desirably at least 50% more, than thetwo edge regions.

[0046] Similarly, nonwoven web 12 may be formed from a combination ofsubstantially crystalline polypropylene fibers as defined above, andpolypropylene/polyethylene bicomponent fibers. The bicomponent fiberseach contain from 10-90% by weight polypropylene and 10-90% by weightpolyethylene in two distinct phases, suitably 25-75% by weight of eachcomponent in two distinct phases. The bicomponent fibers may have apolypropylene core and a polyethylene sheath, or may have a side-by-sideconfiguration with polypropylene on one side and polyethylene on theother side, or may have an “island-in-the-sea” configuration with adiscontinuous phase of one polymer and a continuous “matrix” phase ofthe other. As explained above, the central region will contain at least20% more, suitably at least 30% more, desirably at least 50% more of thebicomponent fibers based on the total fiber weight in the centralregion, than is contained in the two edge regions. If the edge regionscontain 100% polypropylene fibers and 0% bicomponent fibers, forinstance, the central region should contain at least 20%, suitably atleast 30%, desirably at least 50% of the bicomponent fibers. If the edgeregions contain 70% polypropylene fibers and 30% bicomponent fibers, thecentral region should contain at least 50%, suitably at least 60%,desirably at least 80% of the bicomponent fibers.

[0047] Regardless of which of the above embodiments or variants isselected, the effect is to make the central region 11 of nonwoven web 12relatively easier to neck than the edge regions 11 and 13. This resultsin selectively greater necking in the central region, sufficient toeffect the greater necking in the edge regions which inherently occursduring the conventional necking process. The resulting necked nonwovenweb 22 should have a substantially uniform basis weight. Specifically,the average necked basis weight of the central region should be withinabout ±7% of the average basis weight of the two edge regions, suitablywithin about ≅5% of the average basis weight of the two edge regions,desirably within about ±3% of the average basis weight of the two edgeregions, when the starting nonwoven web is stretched to at least about1.2 times, desirably about 1.25 times its initial length in the machinedirection to cause the necking.

[0048] Another test for uniformity of the necked nonwoven web is basedon measurements of elongation at break in the cross direction, measuredusing ASTM D5034. Samples measuring three inches in the cross directionand one inch in the machine direction are cut inward beginning at bothside edges of the necked nonwoven web. A similar sample is cut preciselyfrom the center of the necked nonwoven web. Each of the samples isplaced in an INSTRON® tester so that one inch of sample is clampedwithin each of the jaws, leaving one inch of cross-directional widthwhich can be stretched when the jaws are extended from each other.

[0049] Again, the necked nonwoven web should have a necked machinedirection length which is at least about 1.2 times, desirably about 1.25times its initial starting length. For the prior art necked nonwovenwebs, there was substantial variation in cross-directional elongation atbreak between the central and edge samples. The edge samples, whichexperienced greater necking, had significantly higher cross directionalelongation at break than the central sample. For purposes of theinvention, both of the edge samples should have a cross-directionalelongation at break which is not more than 20% higher, suitably not morethan 10% higher, desirably not more than 5% higher, than thecross-directional elongation at break of the central sample. Forpurposes of this specification and the accompanying claims, thispercentage difference between the cross-directional elongation at breakof the central sample and the highest cross-directional elongation atbreak of the two edge samples is defined and referred to as “thecross-directional elongation at break nonuniformity index.” Of course,the necked nonwoven web should have a necked width of at least about 9inches, desirably at least about 15 inches, in order for thismeasurement to apply.

[0050] Other aspects of the process of FIG. 1 are conventional, and aredescribed above in the “Background Of The Invention.” A heatingapparatus (not shown), such as an oven, may be positioned between thefirst nip 16 and the second nip 26. The web typically begins neckingbefore entering the oven. The oven can be used to aid in necking andheat setting the entire nonwoven web, resulting in a necked nonwoven web22 which is reversibly necked. The temperature inside the oven should behigh enough to soften the nonwoven fibers and increase their pliability,but not so high as to either a) melt the fibers, or b) soften the fibersto such an extent that the necking process causes significantstretching, narrowing and/or breaking of individual nonwoven fibers.When the nonwoven fibers are made from a polyolefin, for instance, thehighest temperature reached by the nonwoven web inside the oven shouldbe at least about 20° C. below the melting temperature of the fibers,suitably at least about 25° C. below the melting temperature of thefibers, desirably at least about 30° C. below the melting temperature ofthe fibers. Optimal necking temperatures are typically about 30-60° C.below the melting temperature of the fibers. When the nonwoven web is aspunbond polypropylene web, for instance, a desired necking temperatureis about 105-140° C.

[0051] The neckable material 12 may be formed by known nonwovenprocesses, such as, for example, meltblowing processes, spunbondingprocesses or bonded carded web processes and passed directly through thenip 16 without first being stored on a supply roll.

[0052] The neckable material 12 may be a nonwoven material such as, forexample, spunbonded web, meltblown web or bonded carded web. If theneckable material 12 is a web of meltblown fibers, it may includemeltblown microfibers. The neckable material 12 is made from anymaterial that can be treated while necked so that, after treatment, uponapplication of a force to extend the necked material to its pre-neckeddimensions, the material recovers generally to its necked dimensionsupon termination of the force. A method of treatment is the applicationof heat. Certain polymers such as, for example, polyolefins, polyestersand polyamides may be heat treated under suitable conditions to impartsuch memory. Exemplary polyolefins include one or more of polyethylene,polypropylene, polybutene, ethylene copolymers, propylene copolymers andbutene copolymers. Polypropylenes that have been found useful include,for example, polypropylene available from the Himont Corporation underthe trade designation PF-304, polypropylene available from theExxon-Mobil Chemical Company under the trade designation Escorene®PD-3445, and polypropylene available from the Shell Chemical Companyunder the trade designation DX 5A09. Polyethylenes may also be used,including ASPUN® 6811A and 2553 linear low density polyethylenes fromthe Dow Chemical Company, as well as various high density polyethylenes.Chemical characteristics of these materials are available from theirrespective manufacturers.

[0053] In one embodiment of the present invention, the neckable material12 is a multilayer material having, for example, at least one layer ofspunbonded web joined to at least one layer of meltblown web, bondedcarded web or other suitable material. For example, the neckablematerial 12 may be a multilayer material having a first layer ofspunbonded polyolefin having a basis weight from about 0.2 to about 8ounces per square yard (osy), a layer of meltblown polyolefin having abasis weight from about 0.1 to about 4 osy, and a second layer ofspunbonded polyolefin having a basis weight of about 0.2 to about 8 osy.

[0054] Alternatively, the neckable material 12 may be single layer ofmaterial such as, for example, a spunbonded web having a basis weight offrom about 0.2 to about 10 osy or a meltblown web having a basis weightof from about 0.2 to about 8 osy.

[0055] The neckable material 12 may also include a composite materialmade of a mixture of two or more different fibers or a mixture of fibersand particulates. Such mixtures may be formed by adding fibers and/orparticulates to a gas stream in which meltblown fibers are carried sothat an intimate entangled commingling of meltblown fibers and othermaterials (e.g., wood pulp, staple fibers or particulates such as, forexample, superabsorbent materials) occurs prior to collection of thefibers upon a collecting device to form a coherent web of randomlydispersed meltblown fibers and other materials such as disclosed in U.S.Pat. No. 4,100,324, the disclosure of which is hereby incorporated byreference.

[0056] If the neckable material 12 is a nonwoven web of fibers, thefibers should be joined by interfiber bonding using one or more of thebonding processes described in the foregoing “DEFINITION” of interfiberbonding.

[0057] The relation between the original width of the neckable material12 to its width after tensioning determines the stretch limits of thereversibly necked material 22. For example, with reference to FIG. 1 ifit is desired to prepare a reversibly necked material that can bestretched to a 150 percent elongation (i.e., 250 percent of its neckedwidth) and can recover to within about 25 percent of its neckable width,a neckable material having a width “A” such as, for example, 250 cm, istensioned so that it necks down to a width A′ of about 100 cm for apercent neck or percent neckdown of about 60 percent. While tensioned,it is heat treated to maintain its reversibly necked configuration 22.The resulting reversibly necked material has a width A′ of about 100 cmand is stretchable to at least the original 250 cm dimension “A” of theneckable material for an elongation or percent stretch of about 150percent. The reversibly necked material may return to within about 25percent of its necked width of about 100 cm (i.e., to a width of about125 cm) after release of the stretching force for a recover of about 83percent.

[0058] The claims of the present invention are meant to encompassuniformly necked materials which are adapted to stretch at least 75percent in the cross direction, and recover at least 50 percent whenstretched by 75% and then relaxed.

[0059]FIG. 2 schematically illustrates a process 100 for preparing aneck-bonded laminate of the invention, including two necked spunbondedwebs and an elastomeric film between them. In this process, theelastomeric film is extruded between the two necked spunbond webs. Thecentral regions of the spunbond webs 5 have a composition and/orphysical properties designed to selectively enhance necking in thoseregions.

[0060] Referring to FIG. 2, first and second spunbond webs 112 and 212are unwound from supply rolls 101 and 201. First spunbond web 112 passesthrough a first nip 16, including nip rollers 114 and 118, turning at afirst surface velocity; and through a second nip 226, including niprollers 224 and 228, turning at a second surface velocity which ishigher than the first surface velocity. Necking of the spunbond webbetween the first nip 116 and second nip 226 is effected by thedifferent surface velocities, and with the aid of oven 129. The oven 129heats the entire nonwoven web to a temperature about 20-60° C. below themelting temperature of the spunbond fibers.

[0061] Second spunbond web 212 passes through a third nip 216 whichincludes nip rollers 214 and 218, turning at a third surface velocity;and through the above-described second nip 226, including nip rollers224 and 228, turning at the second surface velocity. The second surfacevelocity is higher than the third surface velocity, thereby effectingnecking between the nips 216 and 226. As illustrated, the entirenonwoven web 212 is not heated using an oven. However, the secondspunbond web 212 (like the first spunbond web 112) has a central regionhaving physical properties and/or a polymer composition designed toselectively increase the necking of the central region relative to thetwo edge regions.

[0062] To make the neck bonded laminate 230, a molten elastomer isextruded through a die tip 134 to form an extruded elastomeric film 136.The extruded elastomeric film 136 is deposited directly between thetensioned necked spunbond webs 122 and 222, and all three layers arebrought together in the nip 226. The extruded elastomeric film 136 maycontact the necked materials 122 and 222 within about 0.1-1.0 secondafter the film leaves the die tip 134, suitably within about 0.25-0.5seconds, desirably within about 0.3-0.45 seconds.

[0063] The film of elastomer may be extruded at a temperature of fromabout 180-300° C., suitably about 200-250° C.

[0064] Light pressure is applied in the nip 226 to thermally bond theelastomeric film 136 (in a relatively untensioned state) to thetensioned necked, nonwoven webs 212 and 222. The nip rollers 224 and 228may or may not be patterned, need not be heated, and may be chilled(e.g., to a temperature of about 10-30° C.) so as to quench theelastomeric film between the necked spunbond webs. The resultingneck-bonded laminate 230 can be stretched in the cross direction due tothe extendibility of the necked nonwoven webs. Upon relaxation, thelaminate 230 will return substantially to its original manufacturedconfiguration due to the retractive influence of the elastomeric film.Further details pertaining to the manufacture of neck-bonded laminatesusing a molten elastic film are provided in U.S. Pat. No. 5,514,470 toHaffner et al., which is incorporated by reference.

[0065]FIG. 3 illustrates an alternative process 300 for making alaminate of the invention. In this process, a pre-formed extendible orelastic film is combined with a necked nonwoven web. An extendible filmis one which can be stretched like an elastic film, but does notnecessarily retract. The central region of the nonwoven web 312 has apolymer composition and/or physical properties designed to selectivelyincrease the necking in the central region relative to the two edgeregions.

[0066] Referring to FIG. 3, nonwoven web 12 (for example, aspunbond-meltblown-spunbond laminate) is unwound from supply roll 301.Nonwoven web 12 is passed through a first nip 316, including nip rollers314 and 318 turning at a first surface velocity; and a second nip 326,including nip rollers 324 and 328 turning at a second surface velocitywhich is higher than the first surface velocity, to form necked nonwovenweb 322.

[0067] An extendible or elastomeric film 136 is unwound from a supplyroll 130 and is combined, in a substantially untensioned state, with thetensioned, necked nonwoven web 322 by passing both materials through thesecond nip 326. One or both of the rollers 324 and 328 may be heatedusing techniques well known in the art, to effect thermal bondingbetween the extendible or elastic film and the necked nonwoven web.Further details of a process for joining a pre-fabricated film to anecked nonwoven web are provided in U.S. Pat. No. 5,883,028 to Morman etal., which is incorporated by reference. The resulting laminate 330 hascross-directional extendibility due to the influence of the neckednonwoven web. When the extension force is removed, the laminate 330 willreturn substantially to its manufactured configuration if the film iselastic. If the film is merely extendible but not elastic, the laminatewill not significantly recover.

[0068] The film 136 (FIG. 2 or 3) may be made from any material whichmay be manufactured in sheet form. Generally, any suitable extendible orelastomeric film forming resins or blends containing the same may beutilized for the film.

[0069] For example, the film 136 may be made from elastic blockcopolymers having the general formula A-B-A′ where A and A′ are each athermoplastic polymer endblock which contains a styrenic moiety such asa poly (vinyl arene) and where B is an elastomeric polymer midblock suchas a conjugated diene or a lower alkene polymer. The film 136 may beformed from, for example, (polystyrene/poly(ethylenebutylene)/polystyrene) block copolymers available from theShell Chemical Company under the trademark KRATON G. One such blockcopolymer may be, for example, KRATON G-1657.

[0070] Other exemplary elastomeric materials which may be used includepolyurethane elastomeric materials such as, for example, those availableunder the trademark ESTANE from B. F. Goodrich & Co., polyamideelastomeric materials such as, for example, those available under thetrademark PEBAX from the Rilsan Company, and polyester elastomericmaterials such as, for example, those available under the tradedesignation Hytrel from E. I. DuPont De Nemours & Company. Formation ofelastic sheets from polyester elastic materials is disclosed in, forexample, Morman et al. U.S. Pat. No. 4,741,949, hereby incorporated byreference.

[0071] A polyolefin may be used alone to make an extendible film, or maybe blended with the elastomeric polymer to improve the processability ofthe film composition. The polyolefin must be one which, when subjectedto an appropriate combination of elevated pressure and elevatedtemperature conditions, is extrudable, alone or in blended form. Usefulpolyolefin materials include, for example, polyethylene, polypropyleneand polybutene, including ethylene copolymers, propylene copolymers andbutene copolymers. A particularly useful polyethylene may be obtainedfrom the U.S.I. Chemical Company under the trade designation PetrothaeneNA601 (also referred to herein as PE NA601 or polyethylene NA601). Twoor more of the polyolefins may be utilized. Extrudable blends ofelastomeric polymers and polyolefins are disclosed in, for example,Wisneski et al. U.S. Pat. No. 4,663,220, hereby incorporated byreference.

[0072] The film 136 may also be a pressure sensitive elastomer adhesivesheet. For example, the elastic material itself may be tacky or,alternatively, a compatible tackifying resin may be added to theextrudable elastomeric compositions described above to provide anelastomeric sheet that can act as a pressure sensitive adhesive, e.g.,to bond the elastomeric sheet to a tensioned, necked nonelastic web. Inregard to the tackifying resins and tackified extrudable elastomericcompositions, note the resins and compositions as described in J. S.Keiffer and T. J. Wisneski U.S. Pat. No. 4,789,699, filed Oct. 15, 1986for “Ambient Temperature Bondable Elastomeric Nonwoven Web,” thedisclosure of which is hereby incorporated by reference.

[0073] Any tackifier resin can be used which is compatible with theelastomeric polymer and can withstand the high processing (e.g.,extrusion) temperatures. If blending materials such as, for example,polyolefins or extending oils, are used, the tackifier resin should alsobe compatible with those blending materials. Generally, hydrogenatedhydrocarbon resins are preferred tackifying resins, because of theirbetter temperature stability. REGALREZ™ and ARKON™ P series tackifiersare examples of hydrogenated hydrocarbon resins. ZONATAKT™501 lite is anexample of a terpene hydrocarbon. REGALREZ hydrocarbon resins areavailable from Hercules Incorporated. ARKON P series resins areavailable from Arakawa Chemical (U.S.A.) Incorporated. Of course, thepresent invention is not limited to use of such three tackifying resins,and other tackifying resins which are compatible with the othercomponents of the composition and can withstand the high processingtemperatures, can also be used.

[0074] A pressure sensitive elastomer adhesive may include, for example,from about 40 to about 80 percent by weight elastomeric polymer, fromabout 5 to about 40 percent polyolefin and from about 5 to about 40percent resin tackifier. For example, a particularly useful compositionincluded, by weight, about 61 to about 65 percent KRATON G-1657, about17 to about 23 percent Polyethylene NA-601, and about 15 to about 20percent REGALREZ 1126.

[0075] The film 136 may also be a multilayer material in that it mayinclude two or more individual coherent film layers. If the film iselastic, it may be stretched in the machine direction before beingbonded to the necked nonwoven web 322, to form a laminate which iselastic in both the machine direction and the cross direction. A similarlaminate is disclosed in U.S. Pat. No. 5,116,662, which is incorporatedby reference.

[0076] The laminates of the invention have improved basis weightuniformity due to the improved uniformity of the necked nonwoven webcomponents. When the necked nonwoven webs are stretched to at leastabout 1.2 times, desirably about 1.25 times their initial machinedirection length to cause necking, a laminate of the invention shouldhave an average basis weight in its central region (defined as thecentral 70% of the width of the laminate) which is within about ±7% ofthe average basis weight of the two edge regions (defined as the outer15% of the width on each side of the laminate). Suitably, the averagebasis weight of the central region should be within about ±5% of theaverage basis weight of the two edge regions. Desirably, the averagebasis weight of the central region should be within about ±3% of theaverage basis weight of the two edge regions.

[0077] While the embodiments of the invention disclosed herein arepresently preferred, various modifications and improvements can be madewithout departing from the invention. The scope of the invention isindicated in the appended claims, and all changes that fall within themeaning and range of equivalents are intended to be embraced therein.

We claim:
 1. A neckable nonwoven web, comprising: a central region andtwo edge regions; the central region including a plurality of firstfibers; the two edge regions including a plurality of second fibersdifferent from the first fibers; the fibers in the central and edgeregions being selected so as to provide selectively easier necking inthe central region.
 2. The neckable nonwoven web of claim 1, wherein thefirst fibers have a first areal percentage of interfiber bonding, andthe second fibers have a second areal percentage of interfiber bonding,the second percentage being lower than the first percentage.
 3. Theneckable nonwoven web of claim 2, wherein the first areal percentage ofinterfiber bonding is at least 3% less than the second areal percentageof interfiber bonding.
 4. The neckable nonwoven web of claim 2, whereinthe first areal percentage of interfiber bonding is at least 5% lessthan the second areal percentage of interfiber bonding.
 5. The neckablenonwoven web of claim 2, wherein the first areal percentage ofinterfiber bonding is at least 7% less than the second areal percentageof interfiber bonding.
 6. The neckable nonwoven web of claim 1, whereinthe central region comprises elongated interfiber bonds oriented more ina machine direction, and the two edge regions comprise interfiber bondsoriented more in a cross direction.
 7. The neckable nonwoven web ofclaim 1, wherein the central region comprises interfiber point bondsthat are relatively large and widely spaced, and the two edge regionscomprise interfiber point bonds that are relatively small and closelyspaced.
 8. The neckable nonwoven web of claim 1, wherein the fibers inthe central region have a first average denier, and the fibers in theedge regions have a second average denier, the first average denierbeing smaller than the second average denier.
 9. The neckable nonwovenweb of claim 8, wherein the first average denier is at least 5% smallerthan the second average denier.
 10. The neckable nonwoven web of claim8, wherein the first average denier is at least 10% smaller than thesecond average denier.
 11. The neckable nonwoven web of claim 8, whereinthe first average denier is at least 20% smaller than the second averagedenier.
 12. The neckable nonwoven web of claim 1, wherein the fibers inthe central region are relatively more randomly or cross-directionallyoriented, and the fibers in the two edge regions are relatively moremachine-direction oriented.
 13. The neckable nonwoven web of claim 1,wherein the fibers in the two edge regions are more aligned than thefibers in the central region.
 14. The neckable nonwoven web of claim 1,wherein the fibers in the central region have a first average aspectratio, the fibers in the two edge regions have a second average aspectratio, and the first average aspect ratio is less than the secondaverage aspect ratio.
 15. The neckable nonwoven web of claim 14, whereinthe first average aspect ratio is at least about 0.5 less than thesecond average aspect ratio.
 16. The neckable nonwoven web of claim 14,wherein the first average aspect ratio is at least about 0.75 less thanthe second average aspect ratio.
 17. The neckable nonwoven web of claim14, wherein the first average aspect ratio is at least about 1.0 lessthan the second average aspect ratio.
 18. The neckable nonwoven web ofclaim 1, wherein the fibers in the central region have a first averagebulk density, the fibers in the two edge regions have a second averagebulk density, and the first average bulk density is less than the secondaverage bulk density.
 19. The neckable nonwoven web of claim 18, whereinthe first average bulk density is at least about 5% less than the secondaverage bulk density.
 20. The neckable nonwoven web of claim 18, whereinthe first average bulk density is at least about 10% less than thesecond average bulk density.
 21. The neckable nonwoven web of claim 18,wherein the first average bulk density is at least about 20% less thanthe second average bulk density.
 22. The neckable nonwoven web of claim1, wherein the first fibers are not crimped, the second fibers arecrimped, and the second fibers are present in the edge regions at apercentage at least 10% higher than in the central region.
 23. Theneckable nonwoven web of claim 22, wherein the second fibers are presentin the edge regions of a percentage at least 20% higher than in thecentral region.
 24. The neckable nonwoven web of claim 1, wherein thefirst fibers have a first polymer composition, the second fibers have asecond polymer composition different from the first polymer composition,and the fibers in the central region have, on average, less stiffnessthan the fibers in the two edge regions.
 25. The neckable nonwoven webof claim 24, wherein the first fibers are present in the central regionat a percentage at least about 20% higher than in the two edge regions.26. The neckable nonwoven web of claim 24, wherein the first fibers arepresent in the central region at a percentage at least 30% higher thanin the two edge regions.
 27. The neckable nonwoven web of claim 24,wherein the first fibers are present in the central region at apercentage at least 50% higher than in the two edge regions.
 28. Theneckable nonwoven web of claim 24, wherein the first fibers comprise anethylene-propylene copolymer and the second fibers comprisepolypropylene.
 29. The neckable nonwoven web of claim 24, wherein thefirst fibers comprise polyethylene and the second fibers comprisepolypropylene.
 30. The neckable nonwoven web of claim 24, wherein thefirst fibers comprise polypropylene/polyethylene bicomponent fibers andthe second fibers comprise polypropylene.
 31. A necked nonwoven webhaving a length which is at least about 1.2 times an initial pre-neckedlength, comprising: a central region and two edge regions; the centralregion including a plurality of first fibers and having a first averagebasis weight; the two edge regions including a plurality of secondfibers different from the first fibers and having a second average basisweight; the first basis weight being within about ±7% of the secondbasis weight.
 32. The necked nonwoven web of claim 31, wherein the firstbasis weight is within about ±5% of the second basis weight.
 33. Thenecked nonwoven web of claim 31, wherein the first basis weight iswithin about ±3% of the second basis weight.
 34. A necked nonwoven webhaving a necked width of at least about nine inches, a length which isat least about 1.2 times an initial, pre-necked length, and across-directional nonuniformity index of not more than 20%.
 35. Thenecked nonwoven web of claim 34, wherein the cross-directionalnonuniformity index is not more than 10%.
 36. The necked nonwoven web ofclaim 34, wherein the cross-directional nonuniformity index is not morethan 5%.
 37. The necked nonwoven web of claim 34, comprising a neckedspunbond web.
 38. The necked nonwoven web of claim 34, comprising anecked meltblown web.
 39. The necked nonwoven web of claim 34,comprising a necked spunbond-meltblown-spunbond web laminate.
 40. Thenecked nonwoven web of claim 34, wherein the first fibers have a firstareal percentage of interfiber bonding, and the second fibers have asecond areal percentage of interfiber bonding, the second percentagebeing less than the first percentage.
 41. The necked nonwoven web ofclaim 34, wherein the first fibers have a relatively less restrictiveinterfiber bond pattern, and the second fibers have a relatively morerestrictive interfiber bond pattern.
 42. The necked nonwoven web ofclaim 34, wherein the fibers in the central region have a first averagedenier, and the fibers in the edge regions have a second average denier,the first average denier being less than the second average denier. 43.The necked nonwoven web of claim 34, wherein the fibers in the centralregion are relatively more randomly or cross-directionally oriented, andthe fibers in the two edge regions are relatively more machine-directionoriented.
 44. The necked nonwoven web of claim 34, wherein the fibers inthe central region have a first average aspect ratio, the fibers in thetwo edge regions have a second average aspect ratio, and the firstaverage aspect ratio is less than the second average aspect ratio. 45.The necked nonwoven web of claim 34, wherein the fibers in the centralregion have a first average bulk density, the fibers in the two edgeregions have a second average bulk density, and the first average bulkdensity is less than the second average bulk density.
 46. The neckednonwoven web of claim 34, wherein the first fibers are not crimped, andthe second fibers are crimped.
 47. The necked nonwoven web of claim 34,wherein the first fibers have a first polymer composition and the secondfibers have a second polymer composition different from the firstpolymer composition.
 48. The necked nonwoven web of claim 34, whereinthe fibers in the two edge regions are more aligned than the fibers inthe central region.
 49. A laminate, comprising: a necked nonwoven webincluding a central region and two edge regions; the central region ofthe web including a plurality of first fibers; the two edge regions ofthe web including a plurality of second fibers different from the firstfibers; and an elastomeric or extendible film bonded to the neckednonwoven web; wherein the neck-bonded laminate includes a central regionhaving a first basis weight, and two edge regions having a second basisweight within ±7% of the first basis weight.
 50. The neck-bondedlaminate of claim 49, comprising two of the necked nonwoven webs, thefilm being bonded to both necked nonwoven webs.